1. Field of the Invention
The present invention relates to an ESD (Electrostatic Discharge) protection device and a method for manufacturing the same, and in particular, relates to improvement of a discharge auxiliary electrode provided to promote an electrostatic discharge in an ESD protection device.
2. Description of the Related Art
The techniques of interest to the present invention include, for example, those described in Japanese Unexamined Patent Application Publication No. 2007-265713 (Patent Document 1).
Patent Document 1 describes an electrostatic countermeasure component which includes at least two lead electrodes provided on a ceramic substrate to face each other and an electrostatic protection material layer provided so as to cover the parts of those lead electrodes and an area located therebetween, and the electrostatic protection material layer is formed from an electrostatic protection material paste which contains a resin and metal grains provided with passive layers at least on the surfaces thereof and which is prepared by mixing those mentioned above.
The electrostatic protection material layer described above is a layer to enhance an effect of suppressing static electricity, that is, in other words, to promote an electrostatic discharge. However, the electrostatic countermeasure component disclosed in Patent Document 1 has a problem in that the discharge starting voltage and the peak voltage cannot be easily decreased. In addition, when static electricity is repeatedly applied, degradation in characteristics, such as increase in discharge starting voltage and peak voltage, may also disadvantageously occur. That is, there has been a problem in that the discharge starting voltage and the peak voltage cannot be easily controlled. The reason for this is that since the thickness of the passive layer formed on the surface of each metal grain contained in the electrostatic protection material layer is relatively small, when static electricity is repeatedly applied thereto, the passive layer is liable to be fractured, and as a result, a short circuit defect occurs.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2007-265713